This project identifies and characterizes biochemical mechanisms for dopamine receptors and beta-adrenoceptors. The knowledge of basic biochemical phenomena involved with these two receptors permits a better understanding of the mechanism of action of drugs used to treat Parkinson's disease. Among the topics pursued in the current fiscal year are: 1) the identification of GTP and GDP as components of the brain which are responsible for the expression of the hormone-sensitivity of the beta-adrenoceptor and the D-1 dopamine receptor. The presence of these endogenous constituents of the brain permit the expression of hormone-sensitivity of the adenylate cyclase activity; 2) a detailed study of the regulation of alpha-melanocyte stimulating hormone (alpha-MSH) release from the intermediate lobe of the rat pituitary; and 3) the identification of biochemical effects of the dopaminergic ergots.